The invention relates to a back flow prevention system for the protection of the watermain, with particular application in dental clinics.
In dental clinics, and in particular during dental bridgework, it is frequently necessary to use water from the watermain; a typical instance, which will be used during the following description and which is to be considered not as an indication of the limits of the back flow prevention system but purely as an apt example, is the liquid ring pump in aspirating dental instruments. These pumps are used to aspirate fluids that naturally abound in bacteria and pollutants. For this reason it is absolutely necessary, and in many cases a legal requirement, to prevent these bacteria and pollutants from getting into the watermain; this can happen both in cases of malfunction of the pump (for example, through accidental function inversion) and during times when the pump is not in use.
In order to avoid such accidents filters are sometimes used, which are quite effective as regards pollutants, but which produce unsatisfactory results as far as bacterial pollution is concerned. Also used for this purpose are complex-type valves which prevent the return of the fluid towards the watermain in the case of siphoning or flow inversion. However, these valves do not guarantee absolute security with regard to halting the bacteria which, even if only in certain circumstances, can reach the watermain.